docs: def get_asset_metadata(self, did):
          """
          Retrieve asset metadata for a given did.
  
          :param did: Asset DID string
          :return: metadata key of the DDO instance
          """
          response = self.requests_session.get(f'{self._base_url}/metadata/{did}').content
          if not response:
              return {}
          try:
              parsed_response = json.loads(response)
          except TypeError:
              parsed_response = None
          except ValueError:
              raise ValueError(response.decode('UTF-8'))
          if parsed_response is None:
              return {}
          return parsed_response['metadata']